ACT I: Lieutenant Pinkerton of the U.S. Navy inspects a house overlooking Nagasaki harbor. Goro, who is brokering his marriage to Cio-Cio-San, shows him around and introduces him to the cook and his future wife’s maid, Suzuki. The American consul Sharpless arrives out of breath from climbing the hill. Pinkerton describes his philosophy of the roving Yankee in search of pleasure wherever he can find it. (“Dovunque al mondo”). After sending Goro to bring his bride, who is also known as Madame Butterfly, Pinkerton expounds on his infatuation with her. Sharpless warns that she may have other ideas about the marriage and he hopes that Pinkerton doesn’t hurt her. Pinkerton brushes aside his friend’s concerns and raises a toast to America (“America forever!”) and the day he will have a real American wife.

Goro returns leading Butterfly and her friends in a procession up the hill. Butterfly bows to Pinkerton and Sharpless.  She tells Sharpless that she is 15 years old and that her family was once prominent but lost its position. Now she has had to earn her living as a geisha. As Butterfly’s family arrives, she shows Pinkerton her few and treasured possessions and tells him that she has visited the American mission to renounce her ancestral religion and embrace his. The Imperial Commissioner proclaims the marriage and the couple is congratulated. But the festivities are interrupted by the Bonze, Butterfly’s uncle, a Buddhist priest. He curses Butterfly for dismissing her religion. After ordering everyone to leave, Pinkerton attempts to comfort his bride and the lovers embrace (“Viene la sera”).

ACT II, Scene 1: Three years later. With Suzuki by her side, Butterfly waits for her husband’s return, which he has promised will be ‘when the robin builds his nest again.’ Butterfly imagines his return and the joy it will bring (“Un bel dì”). Sharpless arrives with a letter from Pinkerton but on his heels is Goro with a potential husband for Butterfly, the wealthy Prince Yamadori. Butterfly rejects the offer of marriage and after Yamadori and Goro leave, Sharpless begins to read the letter, which says that Pinkerton will not return to Butterfly. When Sharpless suggests that she reconsider Yamadori’s offer, Butterfly furiously fetches her small child and asks “And this?” (“E questo?”) Too astonished to tell her more from the letter, Sharpless leaves, promising to tell Pinkerton of the child. A cannon shot from the harbor signals the arrival of a ship and, when Butterfly and Suzuki grab a telescope and read the name of Pinkerton’s ship, they are overwhelmed. After Butterfly and Suzuki gather blossoms and scatter petals throughout the home (“Squoti quella fronda”), they sit with the child into night, waiting for Pinkerton while keeping watch over the harbor.

ACT II, Scene 2: As dawn arrives, Butterfly sings a lullaby and takes the child to another room where they both fall asleep. Pinkerton arrives with Sharpless and, when Suzuki asks about the identity of the woman with them, Sharpless says that it is Pinkerton’s new wife, Kate. They want to make sure that the child has a good American upbringing. Pinkerton expresses his grief and the guilt he feels for abandoning Butterfly, and leaves unable to face her (“Addio, fiorito asil”). When Butterfly rushes in and realizes the situation, she agrees to give them her child, but only on the condition that Pinkerton will return to get him. After everyone leaves, Butterfly takes her father’s dagger and, after bidding farewell to her child (“Tu? Tu? Piccolo iddio”), stabs herself as Pinkerton desperately calls her name.